Area Calculator

Using the calculator is simple. Start by selecting the shape you're working with, then enter the required measurements in the input fields. The calculator will display the area instantly, usually in square units matching whatever unit you used for the dimensions.

A few things worth keeping in mind:

• Make sure all your measurements are in the same unit before entering them. Mixing inches and feet, for example, will give you a wrong answer.
• Use decimal values when you need precision. Most fields accept decimals just fine.
• If you're not sure which formula applies to your shape, scroll down to the shape-specific sections below for a quick explanation.

The calculator covers rectangles, squares, circles, triangles, trapezoids, parallelograms, ellipses, and sectors. If your shape is irregular, try breaking it into simpler shapes and adding the areas together.

A rectangle is one of the most common shapes you'll deal with in real life, from rooms and yards to screens and pieces of paper. The area is simply the product of its two side lengths.

Formula: Area = Length × Width

Enter the length and width of the rectangle, and the calculator returns the area in square units. For example, a room that's 12 feet long and 10 feet wide has an area of 120 square feet. That's the number you'd use when buying flooring, paint, or carpet.

Keep in mind that a rectangle has four right angles and opposite sides of equal length. If your shape has sides of four different lengths or no right angles, it's not a rectangle, and you'd need a different approach.

A square is really just a special rectangle where all four sides are the same length. So the formula simplifies nicely.

Formula: Area = Side × Side, or Side²

Just enter the length of one side. The calculator squares it and gives you the area. A square with sides of 7 meters, for instance, has an area of 49 square meters.

Squares come up a lot in tile work, fabric cutting, and land plots. If someone tells you a property is a "quarter-acre square lot," you can work backward from the area to figure out the side length too.

Circles are everywhere: pipes, wheels, pools, pizza. The area formula involves pi (π), which is approximately 3.14159. You can calculate circle area using either the radius or the diameter, depending on which measurement you have handy.

Triangles are a bit more variable than rectangles or circles because they come in so many different shapes. There are two main approaches to calculating triangle area, and which one you use depends on what measurements you actually have.

A trapezoid has four sides, but only two of them are parallel. Those two parallel sides are called the bases, and the distance between them is the height.

Formula: Area = ((Base₁ + Base₂) / 2) × Height

Basically, you're averaging the two parallel sides and then multiplying by the height. A trapezoid with bases of 6 and 10 feet, and a height of 4 feet, has an area of 32 square feet.

Trapezoids show up in architecture, land surveying, and graphic design more often than you might expect. If you're calculating the area of a cross-section, a roof section, or a sloped piece of land, there's a good chance you're dealing with a trapezoid.

A parallelogram looks like a slanted rectangle. Opposite sides are parallel and equal in length, but the corners aren't necessarily right angles. The area formula is similar to a rectangle's, with one key distinction: you use the perpendicular height, not the slant side length.

Formula: Area = Base × Height

The height here is the vertical distance between the two parallel bases, measured at a right angle. If you use the slanted side length instead, you'll get a larger (and incorrect) answer.

A parallelogram with a base of 9 meters and a perpendicular height of 4 meters has an area of 36 square meters. Enter those two values into the calculator and you're set.

These two shapes are a little less common in everyday projects but come up often in engineering, design, and math coursework.

An ellipse is basically a stretched circle. It has two radii: the semi-major axis (the longer one, often called a) and the semi-minor axis (the shorter one, often called b).

Ellipse Formula: Area = π × a × b

A sector is a pie-slice portion of a circle. To calculate its area, you need the radius of the full circle and the central angle of the slice.

Sector Formula: Area = (θ / 360) × π × r² (when θ is in degrees)

For example, a sector with a radius of 6 inches and a central angle of 90 degrees is a quarter circle, so its area is one-quarter of the full circle's area, which is about 28.27 square inches. The calculator accepts the angle in degrees and handles the conversion automatically.

Here's a quick reference table for all the shapes covered in this calculator. Bookmark it or screenshot it for when you need a fast reminder.

Sometimes seeing the numbers worked out helps things click. Here are a few practical examples across different shapes.

• Bedroom flooring: A rectangular room that's 14 feet by 11 feet has an area of 154 square feet. That's how much flooring material you'd need before accounting for waste and cuts.
• Circular garden bed: A round garden with a radius of 3 feet has an area of about 28.27 square feet. Useful for figuring out how much mulch or soil to buy.
• Triangular plot of land: A triangle with a base of 20 meters and a height of 15 meters covers 150 square meters.
• Trapezoidal countertop: A countertop with parallel edges of 4 feet and 6 feet, and a depth of 2 feet, has an area of 10 square feet.
• Elliptical table surface: An ellipse with a semi-major axis of 3 feet and a semi-minor axis of 2 feet has an area of about 18.85 square feet.

These examples use common units, but the same formulas work with any consistent unit. Just make sure you don't mix centimeters and inches in the same calculation.

Area is expressed in square units, so conversions aren't as simple as multiplying a single factor. When you convert a length, you're dealing with one dimension. Area has two, so the conversion factor gets squared.

For example, 1 foot equals 12 inches. But 1 square foot equals 144 square inches (12 × 12). That trips people up all the time.

Here are some common area unit conversions:

If you're working on a home improvement project in the US, square feet is probably your default unit. For scientific or international work, square meters is the standard. And for large land areas, you'll typically see acres (US) or hectares (metric).

When in doubt, convert everything to one unit before you start calculating. It's a small step that prevents a lot of headaches.